NSWP: Formation and Characteristics of the Harang Reversal and Relations to Substorms: Simulations with the Rice Convection Model

在被称为哈朗不连续的区域，电离层电场方向的反转在电离层和磁层的大尺度动力学中起着重要的作用。本项目利用Rice对流模式（RCM）模拟哈朗反转，以评估其形成和特征的物理过程，以及其在次暴期间的演变。RCM可以适当地考虑等离子体在等离子体片内漂移输运的物理特性，并通过场向电流耦合解决电离层电势与等离子体片动力学自一致的问题。这个项目将进一步发展模拟，使其更加逼真。磁场求解器将提供与RCM等离子体压力相平衡的磁场。将利用Geotail卫星的观测资料建立粒子边界条件。该组合模型将用于对据信控制哈朗反转的物理过程进行定量评估。模拟的定量结果将与地面雷达观测结果进行比较。为了评估潜在的物理过程，模型中的单个物理参数将发生变化，以观察这些变化如何影响哈朗反转。在保持其他参数不变的情况下，通过改变单个参数，将有可能确定每个参数对哈朗反转的形成和特征的影响。为了了解哈朗倒转与磁亚暴之间的关系并检验亚暴理论，本项目将评估哈朗倒转的演变及其在亚暴生长阶段和等离子体片对流强烈减少后的初始阶段与等离子体片的相关性。该项目将检验对流电场的减少是否会像理论预测的那样导致越来越快的变化和不稳定性。模拟将首次提供哈朗反转的定量评估，它与等离子体片的相关性，它在亚暴期间对行星际条件变化的演变和响应，以及它在预测亚暴方面的潜在用途，这将对理解等离子体片内磁层-电离层耦合和亚暴触发至关重要。

The reversal in the direction of the ionospheric electric field in the region known as the Harang discontinuity is known to play an important role in the large-scale dynamics of the ionosphere and magnetosphere. This project uses the Rice Convection Model (RCM) to simulate the Harang reversal in order to evaluate the physical processes responsible for its formation and characteristics, as well as its evolution during substorms. The RCM can appropriately take into account the physics of the plasma drift transport within the plasma sheet, and it solves for the ionospheric electric potential self-consistently with the plasma sheet dynamics through their coupling by field-aligned currents. This project will further develop simulations to be more realistic. A magnetic field solver will provide magnetic fields that are in force balance with the RCM plasma pressures. Particle boundary conditions will be established using observations from the Geotail satellite. This combined model will be used to provide quantitative evaluation of the physical processes believed to govern the Harang reversal. The quantitative results from the simulations will be compared with ground-based radar observations. To evaluate the underlying physical processes, individual physical parameters in the model will be varied to see how the variations effect the Harang reversal. By varying a single paramter while keeping others fixed it will be possible to determine the effect of each parameter on the formation and characteristics of the Harang reversal. To understand the relationship between the Harang reversal and magnetic substorms and to test a substorm theory, this project will evaluate the evolution of the Harang reversal and its correlations to the plasma sheet during the substorm growth phase and during the initial stage after a strong decrease in plasma sheet convection. The project will examine whether or not a decrease in the convective electric field leads towards increasingly rapid changes and instability as predicted by the theory. The simulations will be the first to provide quantitative assessment of the Harang reversal, its correlations with the plasma sheet, its evolution and response to variations of interplanetary conditions during substorms, and its potential use to predict substorms, which will be crucial to understanding magnetosphere-ionosphere coupling within the plasma sheet and substorm triggering.